Safer train stations with 3D technology

Computational fluid dynamics (CFD) measures wind pressure at railway stations, ensuring passengers are not knocked off their feet. It can save time and money too.

Credit: Katinka Hustad

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By Michael Rothenborg, May 2017

Had Holmestrand Station been completed according to its initial design, passengers would have literally been blown away. Trains passing through the Norwegian mountain where the station is located can reach speeds of over 150 km/h – meaning a wind pressure of 15 metres per second in the access tunnel, which makes it very difficult for someone to stand upright.

Ramboll discovered this using CFD as a planning tool. And this is just one of many examples of how this 3D technology can significantly benefit clients and society in general.

“Just as meteorologists can predict the weather, we can use CFD to predict how the wind will blow, how smoke will move and what happens when a train passes into and out of a tunnel,” explains Jens Christian Bennetsen, Senior Project Manager at Ramboll Transport.

He has worked with CFD for over 20 years, initially on projects with building interiors where the technology helped to dimension ventilation systems and optimise fire safety. This gradually extended to other areas like urban planning in Hong Kong and baseball stadiums in the USA. For well over 10 years, the technology has been a fellow passenger on some of the most advanced railway and high-speed train projects in the Nordics.

A wind-proof station

“We can base the design on facts and optimise it to make it cheaper, while also more accurately taking into account security requirements from authorities, price requirements from operators and other factors. This also helps prevent unnecessary costs after commissioning because the design requires less adaptation than usual. This reduces the project risk.”

In Norway, Ramboll proposed enclosing Holmestrand station and the access tunnel with a wind-proof lock with two doors at each end. When the station opened to the public in November 2016, it was free of wind pressure problems. And the stakeholders were impressed:

“Never before have we built a station inside a mountain with trains running at such high speeds,” said Knut Edmund Knutsen, Project Manager at Jernbaneverket to the Norwegian industry magazine Byggeindustrien.

Ramboll is working on a similar project in Sweden, where the new Barkeby station is also located in a tunnel. Ramboll experts have recommended designing platform screen doors to protect passengers from wind and to improve ventilation.

More precise measurements

CFD is also becoming more relevant in Denmark, which is phasing in high-speed trains. Ramboll has examined all the small tunnels on the new railway line between Copenhagen and Ringsted, part of the Fehmarn Belt fixed link project to connect Denmark and Germany, and has also done calculations on a tunnel under Vejle Fjord. The findings from these projects show that the more precise calculations enabled by CFD open the possibility of building narrower tunnels.

“Without CFD you often act conservatively, making the diameter of the tunnel larger – too large, in fact – and thus putting more concrete in the tunnel. With CFD, we get detailed insight and data that can save time and money on these parameters,” Jens Christian Bennetsen points out.

While CFD calculations obviously come at a cost, they pay off in the long run, especially when combined with high-performance computing. These aerodynamic analyses often provide insights that can be used in a number of other areas. At Holmestrand Station, for example, Ramboll and Jernbaneverket obtained knowledge about not only the wind pressure in the tunnel but also ventilation and antifreeze precautions.

”CFD can find the optimal balance between laws, rules and requirements, on the one hand, and the operator’s demand for value-for-money on the other,” says Jens Christian Bennetsen.